// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Copied from strings/stringpiece.h with modifications
//
// A string-like object that points to a sized piece of memory.
//
// You can use StringPiece as a function or method parameter.  A StringPiece
// parameter can receive a double-quoted string literal argument, a "const
// char*" argument, a string argument, or a StringPiece argument with no data
// copying.  Systematic use of StringPiece for arguments reduces data
// copies and strlen() calls.
//
// Prefer passing StringPieces by value:
//   void MyFunction(StringPiece arg);
// If circumstances require, you may also pass by const reference:
//   void MyFunction(const StringPiece& arg);  // not preferred
// Both of these have the same lifetime semantics.  Passing by value
// generates slightly smaller code.  For more discussion, Googlers can see
// the thread go/stringpiecebyvalue on c-users.

#ifndef BASE_STRINGS_STRING_PIECE_H_
#define BASE_STRINGS_STRING_PIECE_H_

#include <stddef.h>

#include <iosfwd>
#include <string>

#include "base/base_export.h"
#include "base/logging.h"
#include "base/strings/string16.h"

namespace base {

template <typename STRING_TYPE>
class BasicStringPiece;
typedef BasicStringPiece<std::string> StringPiece;
typedef BasicStringPiece<string16> StringPiece16;

// internal --------------------------------------------------------------------

// Many of the StringPiece functions use different implementations for the
// 8-bit and 16-bit versions, and we don't want lots of template expansions in
// this (very common) header that will slow down compilation.
//
// So here we define overloaded functions called by the StringPiece template.
// For those that share an implementation, the two versions will expand to a
// template internal to the .cc file.
namespace internal {

    BASE_EXPORT void CopyToString(const StringPiece& self, std::string* target);
    BASE_EXPORT void CopyToString(const StringPiece16& self, string16* target);

    BASE_EXPORT void AppendToString(const StringPiece& self, std::string* target);
    BASE_EXPORT void AppendToString(const StringPiece16& self, string16* target);

    BASE_EXPORT size_t copy(const StringPiece& self,
        char* buf,
        size_t n,
        size_t pos);
    BASE_EXPORT size_t copy(const StringPiece16& self,
        char16* buf,
        size_t n,
        size_t pos);

    BASE_EXPORT size_t find(const StringPiece& self,
        const StringPiece& s,
        size_t pos);
    BASE_EXPORT size_t find(const StringPiece16& self,
        const StringPiece16& s,
        size_t pos);
    BASE_EXPORT size_t find(const StringPiece& self,
        char c,
        size_t pos);
    BASE_EXPORT size_t find(const StringPiece16& self,
        char16 c,
        size_t pos);

    BASE_EXPORT size_t rfind(const StringPiece& self,
        const StringPiece& s,
        size_t pos);
    BASE_EXPORT size_t rfind(const StringPiece16& self,
        const StringPiece16& s,
        size_t pos);
    BASE_EXPORT size_t rfind(const StringPiece& self,
        char c,
        size_t pos);
    BASE_EXPORT size_t rfind(const StringPiece16& self,
        char16 c,
        size_t pos);

    BASE_EXPORT size_t find_first_of(const StringPiece& self,
        const StringPiece& s,
        size_t pos);
    BASE_EXPORT size_t find_first_of(const StringPiece16& self,
        const StringPiece16& s,
        size_t pos);

    BASE_EXPORT size_t find_first_not_of(const StringPiece& self,
        const StringPiece& s,
        size_t pos);
    BASE_EXPORT size_t find_first_not_of(const StringPiece16& self,
        const StringPiece16& s,
        size_t pos);
    BASE_EXPORT size_t find_first_not_of(const StringPiece& self,
        char c,
        size_t pos);
    BASE_EXPORT size_t find_first_not_of(const StringPiece16& self,
        char16 c,
        size_t pos);

    BASE_EXPORT size_t find_last_of(const StringPiece& self,
        const StringPiece& s,
        size_t pos);
    BASE_EXPORT size_t find_last_of(const StringPiece16& self,
        const StringPiece16& s,
        size_t pos);
    BASE_EXPORT size_t find_last_of(const StringPiece& self,
        char c,
        size_t pos);
    BASE_EXPORT size_t find_last_of(const StringPiece16& self,
        char16 c,
        size_t pos);

    BASE_EXPORT size_t find_last_not_of(const StringPiece& self,
        const StringPiece& s,
        size_t pos);
    BASE_EXPORT size_t find_last_not_of(const StringPiece16& self,
        const StringPiece16& s,
        size_t pos);
    BASE_EXPORT size_t find_last_not_of(const StringPiece16& self,
        char16 c,
        size_t pos);
    BASE_EXPORT size_t find_last_not_of(const StringPiece& self,
        char c,
        size_t pos);

    BASE_EXPORT StringPiece substr(const StringPiece& self,
        size_t pos,
        size_t n);
    BASE_EXPORT StringPiece16 substr(const StringPiece16& self,
        size_t pos,
        size_t n);

#if DCHECK_IS_ON()
    // Asserts that begin <= end to catch some errors with iterator usage.
    BASE_EXPORT void AssertIteratorsInOrder(std::string::const_iterator begin,
        std::string::const_iterator end);
    BASE_EXPORT void AssertIteratorsInOrder(string16::const_iterator begin,
        string16::const_iterator end);
#endif

} // namespace internal

// BasicStringPiece ------------------------------------------------------------

// Defines the types, methods, operators, and data members common to both
// StringPiece and StringPiece16. Do not refer to this class directly, but
// rather to BasicStringPiece, StringPiece, or StringPiece16.
//
// This is templatized by string class type rather than character type, so
// BasicStringPiece<std::string> or BasicStringPiece<base::string16>.
template <typename STRING_TYPE>
class BasicStringPiece {
public:
    // Standard STL container boilerplate.
    typedef size_t size_type;
    typedef typename STRING_TYPE::value_type value_type;
    typedef const value_type* pointer;
    typedef const value_type& reference;
    typedef const value_type& const_reference;
    typedef ptrdiff_t difference_type;
    typedef const value_type* const_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    static const size_type npos;

public:
    // We provide non-explicit singleton constructors so users can pass
    // in a "const char*" or a "string" wherever a "StringPiece" is
    // expected (likewise for char16, string16, StringPiece16).
    BasicStringPiece()
        : ptr_(NULL)
        , length_(0)
    {
    }
    BasicStringPiece(const value_type* str)
        : ptr_(str)
        , length_((str == NULL) ? 0 : STRING_TYPE::traits_type::length(str))
    {
    }
    BasicStringPiece(const STRING_TYPE& str)
        : ptr_(str.data())
        , length_(str.size())
    {
    }
    BasicStringPiece(const value_type* offset, size_type len)
        : ptr_(offset)
        , length_(len)
    {
    }
    BasicStringPiece(const typename STRING_TYPE::const_iterator& begin,
        const typename STRING_TYPE::const_iterator& end)
    {
#if DCHECK_IS_ON()
        // This assertion is done out-of-line to avoid bringing in logging.h and
        // instantiating logging macros for every instantiation.
        internal::AssertIteratorsInOrder(begin, end);
#endif
        length_ = static_cast<size_t>(std::distance(begin, end));

        // The length test before assignment is to avoid dereferencing an iterator
        // that may point to the end() of a string.
        ptr_ = length_ > 0 ? &*begin : nullptr;
    }

    // data() may return a pointer to a buffer with embedded NULs, and the
    // returned buffer may or may not be null terminated.  Therefore it is
    // typically a mistake to pass data() to a routine that expects a NUL
    // terminated string.
    const value_type* data() const { return ptr_; }
    size_type size() const { return length_; }
    size_type length() const { return length_; }
    bool empty() const { return length_ == 0; }

    void clear()
    {
        ptr_ = NULL;
        length_ = 0;
    }
    void set(const value_type* data, size_type len)
    {
        ptr_ = data;
        length_ = len;
    }
    void set(const value_type* str)
    {
        ptr_ = str;
        length_ = str ? STRING_TYPE::traits_type::length(str) : 0;
    }

    value_type operator[](size_type i) const { return ptr_[i]; }
    value_type front() const { return ptr_[0]; }
    value_type back() const { return ptr_[length_ - 1]; }

    void remove_prefix(size_type n)
    {
        ptr_ += n;
        length_ -= n;
    }

    void remove_suffix(size_type n)
    {
        length_ -= n;
    }

    int compare(const BasicStringPiece<STRING_TYPE>& x) const
    {
        int r = wordmemcmp(
            ptr_, x.ptr_, (length_ < x.length_ ? length_ : x.length_));
        if (r == 0) {
            if (length_ < x.length_)
                r = -1;
            else if (length_ > x.length_)
                r = +1;
        }
        return r;
    }

    STRING_TYPE as_string() const
    {
        // std::string doesn't like to take a NULL pointer even with a 0 size.
        return empty() ? STRING_TYPE() : STRING_TYPE(data(), size());
    }

    const_iterator begin() const { return ptr_; }
    const_iterator end() const { return ptr_ + length_; }
    const_reverse_iterator rbegin() const
    {
        return const_reverse_iterator(ptr_ + length_);
    }
    const_reverse_iterator rend() const
    {
        return const_reverse_iterator(ptr_);
    }

    size_type max_size() const { return length_; }
    size_type capacity() const { return length_; }

    static int wordmemcmp(const value_type* p,
        const value_type* p2,
        size_type N)
    {
        return STRING_TYPE::traits_type::compare(p, p2, N);
    }

    // Sets the value of the given string target type to be the current string.
    // This saves a temporary over doing |a = b.as_string()|
    void CopyToString(STRING_TYPE* target) const
    {
        internal::CopyToString(*this, target);
    }

    void AppendToString(STRING_TYPE* target) const
    {
        internal::AppendToString(*this, target);
    }

    size_type copy(value_type* buf, size_type n, size_type pos = 0) const
    {
        return internal::copy(*this, buf, n, pos);
    }

    // Does "this" start with "x"
    bool starts_with(const BasicStringPiece& x) const
    {
        return ((this->length_ >= x.length_) && (wordmemcmp(this->ptr_, x.ptr_, x.length_) == 0));
    }

    // Does "this" end with "x"
    bool ends_with(const BasicStringPiece& x) const
    {
        return ((this->length_ >= x.length_) && (wordmemcmp(this->ptr_ + (this->length_ - x.length_), x.ptr_, x.length_) == 0));
    }

    // find: Search for a character or substring at a given offset.
    size_type find(const BasicStringPiece<STRING_TYPE>& s,
        size_type pos = 0) const
    {
        return internal::find(*this, s, pos);
    }
    size_type find(value_type c, size_type pos = 0) const
    {
        return internal::find(*this, c, pos);
    }

    // rfind: Reverse find.
    size_type rfind(const BasicStringPiece& s,
        size_type pos = BasicStringPiece::npos) const
    {
        return internal::rfind(*this, s, pos);
    }
    size_type rfind(value_type c, size_type pos = BasicStringPiece::npos) const
    {
        return internal::rfind(*this, c, pos);
    }

    // find_first_of: Find the first occurence of one of a set of characters.
    size_type find_first_of(const BasicStringPiece& s,
        size_type pos = 0) const
    {
        return internal::find_first_of(*this, s, pos);
    }
    size_type find_first_of(value_type c, size_type pos = 0) const
    {
        return find(c, pos);
    }

    // find_first_not_of: Find the first occurence not of a set of characters.
    size_type find_first_not_of(const BasicStringPiece& s,
        size_type pos = 0) const
    {
        return internal::find_first_not_of(*this, s, pos);
    }
    size_type find_first_not_of(value_type c, size_type pos = 0) const
    {
        return internal::find_first_not_of(*this, c, pos);
    }

    // find_last_of: Find the last occurence of one of a set of characters.
    size_type find_last_of(const BasicStringPiece& s,
        size_type pos = BasicStringPiece::npos) const
    {
        return internal::find_last_of(*this, s, pos);
    }
    size_type find_last_of(value_type c,
        size_type pos = BasicStringPiece::npos) const
    {
        return rfind(c, pos);
    }

    // find_last_not_of: Find the last occurence not of a set of characters.
    size_type find_last_not_of(const BasicStringPiece& s,
        size_type pos = BasicStringPiece::npos) const
    {
        return internal::find_last_not_of(*this, s, pos);
    }
    size_type find_last_not_of(value_type c,
        size_type pos = BasicStringPiece::npos) const
    {
        return internal::find_last_not_of(*this, c, pos);
    }

    // substr.
    BasicStringPiece substr(size_type pos,
        size_type n = BasicStringPiece::npos) const
    {
        return internal::substr(*this, pos, n);
    }

protected:
    const value_type* ptr_;
    size_type length_;
};

template <typename STRING_TYPE>
const typename BasicStringPiece<STRING_TYPE>::size_type
    BasicStringPiece<STRING_TYPE>::npos
    =
        typename BasicStringPiece<STRING_TYPE>::size_type(-1);

// MSVC doesn't like complex extern templates and DLLs.
#if !defined(COMPILER_MSVC)
extern template class BASE_EXPORT BasicStringPiece<std::string>;
extern template class BASE_EXPORT BasicStringPiece<string16>;
#endif

// StingPiece operators --------------------------------------------------------

BASE_EXPORT bool operator==(const StringPiece& x, const StringPiece& y);

inline bool operator!=(const StringPiece& x, const StringPiece& y)
{
    return !(x == y);
}

inline bool operator<(const StringPiece& x, const StringPiece& y)
{
    const int r = StringPiece::wordmemcmp(
        x.data(), y.data(), (x.size() < y.size() ? x.size() : y.size()));
    return ((r < 0) || ((r == 0) && (x.size() < y.size())));
}

inline bool operator>(const StringPiece& x, const StringPiece& y)
{
    return y < x;
}

inline bool operator<=(const StringPiece& x, const StringPiece& y)
{
    return !(x > y);
}

inline bool operator>=(const StringPiece& x, const StringPiece& y)
{
    return !(x < y);
}

// StringPiece16 operators -----------------------------------------------------

inline bool operator==(const StringPiece16& x, const StringPiece16& y)
{
    if (x.size() != y.size())
        return false;

    return StringPiece16::wordmemcmp(x.data(), y.data(), x.size()) == 0;
}

inline bool operator!=(const StringPiece16& x, const StringPiece16& y)
{
    return !(x == y);
}

inline bool operator<(const StringPiece16& x, const StringPiece16& y)
{
    const int r = StringPiece16::wordmemcmp(
        x.data(), y.data(), (x.size() < y.size() ? x.size() : y.size()));
    return ((r < 0) || ((r == 0) && (x.size() < y.size())));
}

inline bool operator>(const StringPiece16& x, const StringPiece16& y)
{
    return y < x;
}

inline bool operator<=(const StringPiece16& x, const StringPiece16& y)
{
    return !(x > y);
}

inline bool operator>=(const StringPiece16& x, const StringPiece16& y)
{
    return !(x < y);
}

BASE_EXPORT std::ostream& operator<<(std::ostream& o,
    const StringPiece& piece);

// Hashing ---------------------------------------------------------------------

// We provide appropriate hash functions so StringPiece and StringPiece16 can
// be used as keys in hash sets and maps.

// This hash function is copied from base/strings/string16.h. We don't use the
// ones already defined for string and string16 directly because it would
// require the string constructors to be called, which we don't want.
#define HASH_STRING_PIECE(StringPieceType, string_piece)           \
    std::size_t result = 0;                                        \
    for (StringPieceType::const_iterator i = string_piece.begin(); \
         i != string_piece.end(); ++i)                             \
        result = (result * 131) + *i;                              \
    return result;

struct StringPieceHash {
    std::size_t operator()(const StringPiece& sp) const
    {
        HASH_STRING_PIECE(StringPiece, sp);
    }
};
struct StringPiece16Hash {
    std::size_t operator()(const StringPiece16& sp16) const
    {
        HASH_STRING_PIECE(StringPiece16, sp16);
    }
};

} // namespace base

#endif // BASE_STRINGS_STRING_PIECE_H_
